Research On Methods To Separate Jet Noise From Engine Noise

As the requirements on noise of civil aircraft airworthiness certification becomes higher and higher in recent years, the noise problem of civil aviation engine plays an important role in the design process of the engine. However, the domestic research of aircraft noise and other environmental issues started late, noise airworthiness certification will become one of the important problems that restrict the development of China's civil aviation industry. As China's commercial aircraft engine project started, marking that China's independent innovation of civil aviation engine has entered a substantive operational phase. In order to achieve noise reduction design of engine, it needs to separate the noise of each component from the total engine noise to find the main noise sources and to reduce the noise by component. Therefore, the components noise separation has important significance for noise reduction design of engine. In addition, the noise data of each component obtained by separation methods is an important index to evaluate the performance of engine.Three microphones method based on the engine noise data from three far-field microphones and five microphones method based on the engine noise data from five far-field microphones are studied in this paper. The jet noise separation program is developed using MATLAB, uses engine noise test data of General Electric Company as input data. This program can separate jet noise from total engine noise to obtain the auto-spectra of jet noise sound pressure and to calculate SPL of jet noise.The 1/3 octave sound pressure level(SPL) data of jet noise obtained by separation program can be stored into an Excel form to generate a summary sheet. The variation of jet noise with the angles and the frequency are studied using data visualization function of MATLAB, so as to obtain the directivity and spectrum characteristics of jet noise.Finally, the reliability and accuracy of the separation method is verified by comparing the separation results with the jet noise data of aviation engine manufacturers. The separation methods in this paper have certain reference value to noise airworthiness study of the civil aviation engine.